public class MySingleList implements IList{
    static class ListNode{
        public int val;
        public ListNode next;
        public ListNode(int val){
            this.val=val;
        }
    }
    public ListNode head;
    public void creatList(){
        ListNode node1=new ListNode(1);
        ListNode node2=new ListNode(2);
        ListNode node3=new ListNode(3);
        ListNode node4=new ListNode(4);
        ListNode node5=new ListNode(5);

        node1.next=node2;
        node2.next=node3;
        node3.next=node4;
        node4.next=node5;

        this.head=node1;
    }
    @Override
    public void addFirst(int data) {
        ListNode node=new ListNode(data);
        if(head==null){
            head=node;
        }else{
            node.next=head;
            head=node;
        }
    }

    @Override
    public void addLast(int data) {
        ListNode cur=head;
        ListNode node=new ListNode(data);
        if(head==null){
            head=node;
        }
        else {
            while (cur.next != null) {
                cur = cur.next;
            }
            cur.next=node;
        }
    }

    @Override
    public boolean addIndex(int index, int data) {
        ListNode cur=head;
        ListNode node=new ListNode(data);
        int k=1;
       int s=size();
       if(s<index||index<0) {
           return false;
       }
       if(index==0){
           addFirst(data);
           return true;
       }
       if(index==s){
           addLast(data);
           return true;
       }
           while(k!=index){
               k++;
               cur=cur.next;
           }
           node.next=cur.next;
           cur.next=node;
           return true;

    }

    @Override
    public boolean contains(int key) {
        ListNode cur=head;
        while(cur!=null){
            if(cur.val==key){
                return true;
            }
            cur=cur.next;
        }
        return false;
    }

    @Override
    public void remove(int key) {
        if(head==null){
            return;
        }
        ListNode cur=head;
        if(head.val==key){
            head=head.next;
            return;
        }
        while(cur.next.val!=key){
            cur=cur.next;
            cur.next=cur.next.next;
        }
    }

    @Override
    public void removeAllKey(int key) {
        if(head==null){
            return;
        }
        ListNode prev=head;
        ListNode cur=head.next;
        while(cur!=null){
            if(cur.val==key){
                prev.next=cur.next;
                cur=cur.next;
            }
            else{
                prev=cur;
                cur=cur.next;
            }
        }
        if (head.val == key) {
            head = head.next;
        }
    }

    @Override
    public int size() {
        int k=0;
        ListNode cur=head;

            while(cur!=null){
                k++;
                cur=cur.next;
            }
            return k;
    }

    @Override
    public void display() {
        ListNode cur=head;
        while(cur!=null){
            System.out.print(cur.val+" ");
            cur=cur.next;
        }
        System.out.println();
    }

    @Override
    public void clear() {
        ListNode cur=head;
        while(cur!=null){
            ListNode curNext=cur.next;
            cur=null;
            cur=curNext;
        }
        head=null;
    }
}
